<div class="music-slider" [class.music-slider-vertical]="isVertical" #slider>
  <!-- 水平：width，left; 垂直：heigt,bottom -->
  <app-music-slider-track [vertical]="isVertical" [length]="bufferOffset" [buffer]="true"></app-music-slider-track>
  <app-music-slider-track [vertical]="isVertical" [length]="offset"></app-music-slider-track>
  <app-music-slider-handle [vertical]="isVertical" [offset]="offset"></app-music-slider-handle>
</div>